Sexual Reproduction In Plants: Features and its Process

Sexual reproduction in plants is a natural process that ensures the continuity of a generation. This involves the fusion of male and female gametes to form the embryo, and then the new plant. The process has many stages, such as pollination, fertilisation, embryo development, and seed formation.

Sexual reproduction brings about genetic variation, which makes the plants more adapted for survival in various environments. Stamens and carpels are the reproductive parts of the flower that play an important role in producing and receiving gametes. This process is responsible for the fruits and seeds we see around us. Understanding the process aids in agriculture, horticulture and plant breeding. Sexual reproduction in plants is an important topic in the field of biology.

This Story also Contains

1. What is Sexual Reproduction in Plants?
2. Pollination
3. Pre-Fertilisation Events
4. Fertilisation
5. Post-Fertilisation Events
6. Adaptations for Sexual Reproduction in Plants
7. Recommended video on "Sexual Reproduction in Plants"

What is Sexual Reproduction in Plants?

New plants are produced by the fusion of male and female gametes, which is the process of sexual reproduction of plants. The gametes are formed by the stamens (male) and carpels (female) of the flowering plants. Fertilisation by the fusion of gametes leads to the formation of seeds, which grow into new plants. This method ensures genetic diversity and helps plants survive in a varied environment.

Also Read:

• Multiple Fission
• Reproduction in Organisms
• Asexual Mode of Reproduction

Pollination

Pollination is the process of transferring pollen grains from the male anther to the female stigma of plants. In general, it is divided mainly into two types: self-pollination and cross-pollination. The first one refers to a process within the same flower or any flowers of the same plant that is going to ensures the same genetic makeup. On the other hand, the latter refers to those events that take place between different plants and give rise to genetic variation.

Definition and Types of Pollination

The types of pollination are:

Self-Pollination

Self-pollination occurs when the pollen from the same flower or another flower of the exact plant fertilises the ovules. The process is efficient, as it makes sure that the plant will reproduce in the complete absence of any pollinating agent. It can be autogamy (transfer of pollen from anther to the stigma of the same flower) and geitonogamy (transfer of pollen from anther to the stigma of another flower of the same plant).

Cross-Pollination

Cross-pollination is a process where there is a transfer of pollen to another plant's stigma. The process increases the amount of genetic variation and, hence, improves the resistance of the plant towards pathogenic diseases or even response towards changes in the environment.

Agents of Pollination

Wind

Plants that are wind-pollinated produce large amounts of lightweight pollen to be easily carried by the wind for a considerable distance. Examples include grasses and many trees. It is also known as anemophily.

Water

Plants adapted to water pollination, like some aquatic plants, depend on the flowing water, at least for some time, to carry the pollen to other plants. It is a rare mode of pollination and takes place only in certain aquatic plants.

Animals (Insects, Birds, Bats)

Major animal pollinators are insects, especially bees and butterflies, and some birds and bats. In searching for nectar from one flower to another, they pick up pollen and drop it where it is needed, hence pollinating. Insects, such as bees and butterflies, are attracted to flowers by colour, odour and nectar. While gathering nectar, pollen sticks to the body of the insect and is passively transferred from one flower to another, a process called entomophily. Some flowers are specially adapted to be pollinated by birds. These plants invariably have flowers that are brightly coloured and contain nectar. This is called ornithophily.

Importance of Pollination

Pollination leads to the development of fruits and seeds. It means reproduction in plants, which in turn leads to biodiversity, agriculture, and food production.

Pre-Fertilisation Events

The events include all the processes that happen before the fusion of gametes. These include the development of reproductive structures (stamen and carpel), the formation of the male and female gametes, and pollination. These steps are important to carry out successful fertilisation.

Gametogenesis

It is the process by which the male reproductive structure of the plants forms the male gametes (pollen grains) by the process of microsporogenesis. Megasporogenesis is the process by which the female reproductive structure of the plants forms the female gametes (ovule).

Pollination

It is the process of transferring pollen grains from the male reproductive part (anther) to the female reproductive part (stigma) of plants, enabling the sperm to reach the egg for fertilisation.

Fertilisation

The process of fertilisation in plants includes the following steps: pollen germination on the stigma, growth of the pollen tube in the style, and finally, the fusion of male and female gametes in the ovule.

Process of Fertilisation

The process of fertilisation includes:

Germination of Pollen Grain

After a pollen grain falls on a compatible stigma, it takes up water and the nutrients that stimulate its germination and forms a pollen tube.

Growth of Pollen Tube

The pollen tube grows down the style following the chemical signals and finally reaches the ovule. It takes the male gamete into the ovule to be fertilised.

Fusion of Male and Female Gametes

A male gamete fuses with an egg cell in the ovule to form a zygote, and another one fuses with two polar nuclei to form endosperm, which acts as nutrition to the developing embryo.

Significance of Double Fertilisation in Angiosperms

Double Fertilisation of angiosperms produces the zygote and the endosperm that nourishes the developing embryo. The process ensures the production of food only when the egg is fertilised, without any resource wastage. It results in better coordination between embryo development and nourishment.

Post-Fertilisation Events

The Post-fertilisation events include the development of the zygote into the embryo, and the triploid endosperm forms the embryonic nutritive tissue. Several important events take place in plants to support the development of the embryo. The zygote develops into an embryo, and the ovule transforms into a seed.

Formation of Seed and Fruit

After fertilisation, the ovary of the flower develops into a seed, and the surrounding ovary wall forms the fruit. The fruit protects the seeds as well as aids in their dispersal.

Structure of a Seed

A seed mainly consists of three parts, which are, embryo, endosperm and seed coat. The embryo is the future plant, the endosperm provides nourishment, and the seed coat protects the seed.

Embryo

A young plant inside the seed that develops into a new plant upon germination.

Endosperm

It serves as the food reserve for the embryo. It will supply nutritive factors to the growing plant at the time of germination.

Seed Coat

The seed coat is the outer protective layer that prevents the embryo and endosperm from mechanical damage and desiccation.

Types of Seeds (Monocot and Dicot)

The seeds can be differentiated by the number of cotyledons. In that direction, monocots—like grasses and lilies—have a single cotyledon and dicots—like beans and sunflowers—with two cotyledons.

Adaptations for Sexual Reproduction in Plants

Plants have several adaptation that makes sure sexual reproduction takes place. These adaptations include bright coloured flowers, scent, and nectar to attract the pollinators. Some might have enclosed seeds and special reproductive organs. Some of the adaptations are highlighted below-

Attractants (Colour, Scent)

The colouring of the petals and fragrances in flowers are attractants to the pollinators. The chances of pollination are maximised.

Structural Adaptations

The plants may have some structural features on flowers that favour pollination, such as nectar guides and modified anthers and stigmas that will touch the relevant pollinators.

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